Speed limiting governor for internal combustion engine

ABSTRACT

A speed governor for an internal combustion engine comprises a vibratory reed in the fuel air intake passage of the engine. The reed is arranged in the passageway so that when it is static it does not interfere with fuel air flow to the engine but when it vibrates it periodically blocks the passageway. The natural frequency of the reed corresponds to the desired maximum speed of the engine. When the engine is running at idling speed or normal operating speed the reed remains in static condition. As the engine approaches maximum speed, vibration of the reed is induced by unbalanced forces of the engine and the pulsating fuel air flow through the passageway. When thus set in vibration, the reed partially blocks the passageway to decrease the fuel air flow and thereby limit the engine speed.

United States Patent [1 1 Lombard Nov. 4, 1975 SPEED LIMITING GOVERNOR FOR INTERNAL COMBUSTION ENGINE Ralph S. Lombard, Stamford, Conn.

Assignee: Textron Inc., Providence, RI. Filed: Apr. 18, 1974 Appl. No.: 462,178

Inventor:

References Cited UNITED STATES PATENTS Hanson et a1 261/D1G. 68 Nutten et a1 123/109 X Primary Examiner-Charles J. Myhre Assistant ExaminerWilliam C. Anderson Attorney, Agent, or FirmRobert E. Burns; Emmanuel J. Lobato; Bruce L. Adams [57] ABSTRACT A speed governor for an internal combustion engine comprises a vibratory reed in the fuel air intake passage of the engine. The reed is arranged in the passageway so that when it is static it does not interfere with fuel air flow to the engine but when it vibrates it periodically blocks the passageway. The natural frequency of the reed corresponds to the desired maxi mum speed of the engine. When the engine is running at idling speed or normal'operating speed the reed remains in static condition. As the engine approaches maximum speed, vibration of the reed is induced by unbalanced forces of the engine and the pulsating fuel air flow through the passageway. When thus set in vibration, the reed partially blocks the passageway to decrease the fuel air flow and thereby limit the engine speed.

11 Claims, 2 Drawing Figures U8. Patent Nov. 4, 1975 3,916,853

F/GZ

SPEED LIMITING GOVERNOR FOR INTERNAL COMBUSTION ENGINE FIELD OF INVENTION The present invention relates to a governor for limiting the maximum speed of an internal combustion engine in particular a small lightweight engine.

BACKGROUND OF INVENTION In order to protect an internal combustion engine from the deleterious effects of running at excessive speed it is desirable automatically to limit the speed at which the engine can be operated. The maximum operating speed is selected according to the construction and operating characteristics of the engine so as to provide a useful range of operating speeds while protecting the engine from the excessive wear and destructive stresses incident to excessive speed. Over the years many different devices have been proposed for limiting the speed of internal combustion engines. However, such devices have not been found to be entirely satisfactory. Among the disadvantages of prior devices are complexity of construction, excessive size and weight, unreliability in operation and variation in control speed due to wear or other operating conditions.

SUMMARY OF INVENTION It is an object of the present invention to provide a speed governor for internal combustion engines both two stoke cycle and four stoke cycle engines having the following desirable characteristics:

. Simple construction;

. Low cost;

. Lightweight;

. Small size;

. Precise and easy calibration;

. Easy to install and replace;

. Avoidance of moving parts subject to wear;

. Reliability in operation;

. Uniformity of operation under different operating conditions;

10. Constant operating characteristics throughout life; ll. Less fuel required at governing speed.

In accordance with the invention, the governor for limiting the speed of an internal combustion engine having an intake, a carburetor for supplying a fuel air mixture and a passageway connecting the carburetor with the intake of the engine comprises a flexible reed mounted in the passageway and having a blade which is movable by flexing of the reed between a normal position in which it extends approximately lengthwise of the passageway and a flexed position in which it extends across the passageway so as to at least partially block the passageway. The reed has a natural resonant frequency of vibration corresponding approximately to the selected maximum speed of the engine. When the engine is running at idling speed or at normal operating speed, the reed remains in its normal position extending lengthwise of the passageway. As the engine approaches the selected maximum speed, vibration induced in the reed causes the blade intermittently to block the passageway between the carburetor and the intake of the engine so as to reduce the supply of fuel air mixture to the engine and thereby limit engine speed.

Preferably, the reed has two blades which are approximately parallel to one another in normal unflexed condition. When vibration is induced in the reed the blades cyclically flex outwardly toward the walls of the passageway. Preferably, the blades are contoured so as to conform at least approximately to the opposite walls of the passageway when the blades are flexed outwardly toward the walls. The blades are preferably supported by a support which extends transversely of the passageway and has an opening between the blades so as to permit limited flow of fuel air mixture through the opening. To avoid any noise or wear that might be incident to metal-to-metal contact, nonmetallic cushions are preferably provided in opposite walls of the passageway for engagement by the blades when theyflex outwardly.

BRIEF DESCRIPTION OF DRAWINGS The objects, nature and advantages of the inventi on will appear more fully from the following description of a preferred embodiment shown by way of example in the accompanying drawings in which:

FIG. 1 is a schematic longitudinal section of a governor in accordance with the invention; and 5 FIG. 2 is a schematic longitudinal section taken at right angles to that of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENT In the drawings, there is shown schematically a car buretor 1 for supplying a fuel air mixture to an internal combustion engine 2. The carburetor is shown as having an air inlet passage 3, a fuel jet 4 and a throttle valve 5. It will be understood that the carburetor can be of any usual or desired construction and may for example have a choke valve air regulating valve and other appurtenances not shown in the drawing.

The outlet of the carburetor is connected to the intake 6 of the engine 2 by a passageway 7. The intake is shown as a port which opens into the engine cylinder and is cyclically opened and closed by reciprocation of the piston 8. Alternatively, the intake may open into the crankcase of the engine and may be provided with a reed or other type check valve as is well known in two cycle engines. In any event the rate of flow of fuel air mixture through the passage 7 varies cyclically at a frequency corresponding to the speed of the engine.

The speed governor in accordance with the present invention comprises a flexible reed 10 mounted in the passageway 7 between the carburetor l and the intake 6 of the engine 2. The reed is shown as being of the tuning fork" type with two blades 10a and 10b connected by a base portion 100. The reed is mounted in the passageway by a support 11 which extends transversely across the passageway. The base portion of the reed is secured to the support 11 while the blades 10a and 10b extend in an upstream direction toward the carburetor l. The support 11 and base portion of the reed are shown provided with an opening 12 which permits limited flow of fuel air mixture therethrough.

When the reed is in static unflexed condition the blades 10a and 10b are spaced apart and parallel to one another. When the reed is set in vibration the blades flex outwardly toward opposite walls of the passageway 7 as well as inwardly. The blades of the reed are preferably of a shape to conform at least approximately to the walls of the passageway so that when the blades are flexed outwardly, as shown in broken lines in FIG. 1, they substantially close the passageway except for the opening 12 through the support 11. With a cylindrical passageway as illustrated by way of example in the drawings, the blades are approximately of the shape shown in FIG. 2. To avoid metal-to-metal contact of the blades with the walls of the passageway 7, suitable inserts 14 formed of nonmetallic material, for example an elastomeric material, are provided in the passageway for engagement by the tips of the blades.

When the blades of the reed are in normal position parallel to one another as shown in FIG. 1, they do not substantially interfere with flow of fuel air mixture through the passageway 7. However, as the support 11 obstructs the passageway to some extent, the portion of the passageway which houses the reed is preferably of a larger cross section than the outlet passage of the carburetor so as to compensate for such obstruction. The geometry and material of the reed 10 are selected so that the reed has a natural frequency of vibration corresponding approximately to the selected maximum speed of the engine. As long as the engine is running at a speed appreciably below the selected maximum speed, the reed 10 does not vibrate. Hence, the blades 10a and 10b remain parallel and do not obstruct the flow of fuel air mixture from the carburetor to the engine. However, as the speed of the engine is increased and approaches the selected maximum speed, vibration of the reed is induced by the periodic variation of flow of fuel air mixture through the passageway 7. The mechanical vibration of the engine as it approaches maximum speed may also play a part in inducing resonant vibration ofthe reed. When vibration of the reed is thus induced the blades 10a and 10b of the reed flex outwardly as shown in broken lines in FIG. 1 thereby periodically blocking the flow of fuel air mixture through the passageway except for the restricted opening 12. The supply of fuel air mixture to the engine is thereby decreased so as to limit engine speed. The speed of the engine is thereby automatically limited to a selected value.

The maximum speed of the engine is thus determined by the natural frequency of vibration of the reed 10. This can be selected as desired by varying the material and geometry of the reed. Once the maximum speed of operation of the engine has been selected, it remains constant throughout the life of the engine. As the governor has no moving parts except for the flexing of the reed, its operating characteristics are not altered by friction or by wear. Moreover, as the governor is enclosed in the passageway connecting the carburetor with the intake of the engine, it cannot be tampered with by a user. However, if desired, the reed can be replaced with one having a different natural frequency by disassembling the carburetor and connecting passage from the engine.

While a preferred embodiment of the invention has been shown schematically by way of example in the drawings, it will be understood that many modifications in construction can be made while still retaining the same mode of operation. The invention is hence in no 4 way limited to details of construction as illustrated in the drawings.

What I claim and desire to secure by Letters Patent l. A governor for limiting the speed of an internal combustion engine having means including an intake, passageway for supplying a fuel-air'mixture to the engine, said governor comprising a flexible reed mounted in said passageway and having two blades which are movable by flexing of said reed between a normal unflexed condition in which they are approximately parallel to one another and extend approximately lengthwise of said passageway and a flexed condition in which they extend across said passage so as at least partially to block said passageway, said reed having a natural resonant frequency corresponding approximately to the selected maximum speed of said engine, whereby said reed remains in said normal condition when the engine runs at normal operating speed and is induced to vibrate as the engine approaches saidselected maximum speed, thereby intermittently at least partially blocking said passageway to reduce the fuel-air mixture supplied to the engine and limit engine speed.

2. A governor according to claim 1, in which said blades are contoured so as to conform at least approximately to the opposite walls of said passageway when said blades are flexed outwardly toward said walls. 3. A governor according to claim 1, in which said means for supplying a fuel-air mixture to the engine comprises a carburetor and said passageway connects said carburetor with the engine.

4. A governor according to claim 1, in which the spacing of said blades from one another is approximately twice the spacing of each blade from the nearer side wall of said passageway.

5. A governor according to claim 1, in which nonmetallic cushions are provided in opposite walls of said passageway for engagement by said blades to cushion and quiet the engagement of said blades.

6. A governor according to claim 1, in which said reed is supported by a support extending transversely of said passageway.

7. A governor according to claim 6, in which said support has an opening between said blades to permit limited flow therethrough.

8. A governor according to claim 6 in which said blades extend in an upstream direction from said sup port.

9. A governor according to claim 1, in which said reed is of U-shape comprising said two blades and a base portion joining said blades, said reed being supported in said passageway by said base portion.

10. A governor according to claim 9, in which said blades extend in an upstream direction from said base portion.

11. A governor according to claim 9, in which said base portion is apertured to permit limited flow therethrough. 

1. A governor for limiting the speed of an internal combustion engine having means including an intake, passageway for supplying a fuel-air mixture to the engine, said governor comprising a flexible reed mounted in said passageway and having two blades which are movable by flexing of said reed between a normal unflexed condition in which they are approximately parallel to one another and extend approximately lengthwise of said passageway and a flexed condition in which they extend across said passage so as at least partially to block said passageway, said reed having a natural resonant frequency corresponding approximately to the selected maximum speed of said engine, whereby said reed remains in said normal condition when the engine runs at normal operating speed and is induced to vibrate as the engine approaches said selected maximum speed, thereby intermittently at least partially blocking said passageway to reduce the fuel-air mixture supplied to the engine and limit engine speed.
 2. A governor according to claim 1, in which said blades are contoured so as to conform at least approximately to the opposite walls of said passageway when said blades are flexed outwardly toward said walls.
 3. A governor according to claim 1, in which said means for supplying a fuel-air mixture to the engine comprises a carburetor and said passageway connects said carburetor with the engine.
 4. A governor according to claim 1, in which the spacing of said blades from one another is approximately twice the spacing of each blade from the nearer side wall of said passageway.
 5. A governor according to claim 1, in which nonmetallic cushions are provided in opposite walls of said passageway for engagement by said blades to cushion and quiet the engagement of said blades.
 6. A governor according to claim 1, in which said reed is supported by a support extending transversely of said passageway.
 7. A governor according to claim 6, in which said support has an opening between said blades to permit limited flow therethrough.
 8. A governor according to claim 6 in which said blades extend in an upstream direction from said support.
 9. A governor according to claim 1, in which said reed is of U-shape comprising said two blades and a base portion joining said blades, said reed being supported in said passageway by said base portion.
 10. A governor according to claim 9, in which said blades extend in an upstream direction from said base portion.
 11. A governor according to claim 9, in which said base portion is apertured to permit limited flow therethrough. 